The wild hunt - Spoilers

This is going to be a major spoiler thread so please avoid it if you still playing the game

I am bit confused about the wild hunt and have some random questions,

Both Geralt and Yennefer dies at the end of the books (?). They are brought to life by the girl Ciri(?). They go off and live in an island. Is this bit in the books or they made this up for the game?

The Wild Hunt (elves from another world) takes Yennefer (they want Geralt too but he somehow escape?). Geralt goes in search of her and meet up with Letho and Co. They help him and they eventually find the Wild Hunt (how do they find the hunt?).

Once they find the Hunt, Geralt exchange himself for Yennefer. Why does the Hunt agree for the exchange?

Both Geralt and Yennefer are amnesia after they have been taken by the Hunt. Does it explained why you get that?

Geralt somehow escaped from the Hunt (may be let go). This is the starting point of the first game (?). Do we know how/why? I don't think its explained in W2.